Description: A submersible pressure transducer is the most common sensor used for measuring groundwater level. The sensor measures the head of water above the sensor through the pressure exerted on the sensor head. Components are relatively simple and low cost, only requiring the sensor, cable and conduit to protect the sensor and cable. There are two types of pressure transducers, vented and non-vented. The vented option, has a tube that allows ambient air pressure to be measured by the transducer. The vented systems are then able to subtrct the atmospheric pressure from the static head pressure, thus removing variability due to changes of atmospheric air pressure on the measurement of water level. Vented solutions often require desiccant to keep the transducer free from moisture. The desiccant needs to be changed occassionaly (more often when dew point temperature is high), which can be a maintenance concern. Non-vented pressure transducers operate without directly compensating to atmospheric air pressure. Non-vented sensor or usually less expensive, require less maintenance, along with being less accurate. A third type of pressure transducer is a vented system, but the vented pressure measures the pressure from a bellows system. This solution does not require desiccant, but it generally less accurate than the vented systems to the atmosphere.
Wells may have a nest of submersible pressure transducers that cover various depths of the water table. Operational range of the sensor may vary from 0 to 350m. It is important to select the full-scale range that closely meets your needs. Accuracy is typically based on a percentage of full scale value, therefore the smaller the range the higher accuracy the measurement will be. It is important to avoid a sensor range that is smaller than the maximum water level, this could cause damage to the sensor
Costs USD Lower: $500
Costs USD Upper: $1,500
Accessories: desiccant, contact probe
Advantages: The submersible transducer is ideally suited for ground water. The pressure transducer it easy to install provided there is a proper borehole. Submersible pressure transducers offer internal data logging and power supply
Disadvantages: Sensor requires occasional calibration to chek the instrument linearity
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